CONTROL of ENZYMATIC BROWNING IN RAW FRUIT JUICE BY FILTRATION and CENTRIFUGATION

Filtration and centrifugation were investigated as means of preventing enzymatic browning in minimally processed fruit juices. the capacity of raw apple, grape and pear juices to undergo browning was associated with particulate fractions that could be removed by filtration with Bentonite and/or diatomaceous earth, microfiltration or ultrafiltration, depending on the commodity and cultivar. Centrifugation prevented browning in pear juice and in Granny Smith, Golden Delicious, and Red Delicious but not McIntosh apple juice, provided that foam was excluded and the relative centrifugal force was sufficient. A method for the preparation of nonbrowning, cloudy juices by recombination of juice supernatant or ultrafiltration permeate with particulates, heat-treated to inactivate polyphenol oxidase, was investigated.